This relates generally to semiconductor memories such as flash memories.
Many memories, such as flash memories, are extensively tested in the fabrication facility. If the memory passes those tests, the integrated circuit may be released for sale and use. In some cases, these memories have redundant memory portions which can be activated if one portion of a memory array is defective. Thus, in the fabrication facility, the defective array portion can be activated to replace a defective portion.
However, in many cases, defects do not appear until the product is out in the market. The testing undergone in the fabrication facility cannot duplicate all real life conditions. In addition, some conditions may arise only with sufficient cycling of the memory over time. Cycling or endurance is the ability of the memory to be repeatedly programmed and erased. The inability to continue to operate after a number of cycles is generally termed an endurance failure.
Many integrated circuits, including memories, are used in mission critical applications. In some cases, resources may depend on the accurate operation of the integrated circuit over an extended number of cycles.